Integrated Circuits (ICs) are commonly packaged in surface-mount package types such as a Ball Grid Array (BGA) package. A BGA package is a surface-mount package that utilizes an array of bond balls as the means of providing external electrical interconnection. When such BGA package is used in financial transactions, a thief or hacker may be able to physically penetrate electronic components and gain access to processors, memory devices, and address/data busses that are used to communicate and process sensitive data including passwords, account numbers, pin numbers, access codes, and other information.
To prevent sensitive data from being accessed in an unauthorized manner, various security modules and containers have been developed to enclose a circuit to be protected. A tamper detection circuit within the container is typically connected to a security layer to detect circuit tampering. Once a tamper condition has been detected, sensitive information stored in the circuit is quickly erased before it can be read by the possible attacker. Examples of such security modules are described in U.S. Patent Application Publication. No. 2007/0018334, and in U.S. Patent Application Publication No. 2007/0038865.
FIG. 1 (Prior Art) illustrates a cross-sectional view of a BGA package 1. BGA package 1 includes a substrate member 2 having an anti-tamper security mesh layer 3, an integrated circuit die 4, and an array of bond balls. Six of the bond balls 5-10 are illustrated in the cross-sectional view. Bond balls 5-6 and 9-10 are outer mesh bond balls coupled to anti-tamper security mesh 3, and bond balls 7-8 are inner signal bond balls used for data communication and processing.
FIG. 2 (Prior Art) is a diagram taken along cross-sectional line A-A of FIG. 1. As illustrated in FIG. 2, two rows of outer mesh bond balls are used to prevent possible unauthorized access to one row of inner signal bond balls. However, a thief or hacker may still be able to access the inner signal bond balls by using a thin magnet wire without triggering a tamper condition. Therefore, it is beneficial to make it more difficult for possible attackers to access the inner signal bond balls. It is especially desirable to secure access to the inner signal bond balls designated for security sensitive data transactions.